The incidence of allergic disorders has increased dramatically in the developed world and a variety of factors (e.g. environment, genetics, hygiene, diet) are known to impact on their development. Allergies may start in predisposed individuals from early infancy, e.g. as atopic eczema, limited to or followed by the development of food allergies. Respiratory allergies such as allergic rhinitis and asthma occur later in life and complete the sequel of allergic manifestations. Allergies correspond to a deregulated immune response to a variety of allergens normally present either in the environment, such as dust mite or pollen, or in food, such as milk, eggs, nuts or wheat. Recent advances in the understanding of the pathophysiology of allergy have revealed a series of complex immune cell interactions that could be manipulated to influence either sensitization to the allergen (i.e. prevention) or help to alleviate allergic manifestations and symptoms.
A majority of therapeutic options available today for allergies such as corticosteroids and anti-histaminics are aimed at treating different allergic symptoms. While proven to be highly effective, numerous factors such as dose, route and scheme of administration account for the efficacy of these treatments, notwithstanding the adverse effects that are sometimes associated with a chronic use of these medications.
Nutritional interventions to prevent the development or to manage the symptoms of allergic diseases are a promising alternative to medications and have been assessed in numerous pre-clinical and clinical settings. Typically, the protective effects of probiotic bacteria (Kalliomaki et al., Lancet. 2001, 357:1076-9), prebiotics (Arslanoglu et al. 2008, J Nutr 138:1091-1095) and poly-unsaturated fatty acids (Dunstan et al. 2003, J Allergy Clin Immunol 112: 1178-1184) have been documented. Dietary polyphenols and polyphenol rich plant materials have also been studied extensively in numerous disease models and published data suggest that their presence may have an important role in preventing tissue damage due to oxidative stress and hence might have an anti-allergic potential.
For example, Zurcher et al., 2010, Clinic Exp Allergy, 40(6): 942-50, disclose that polyphenol-enriched apple extract attenuates food allergy in mice. Thereby, consumption of an apple extract particularly rich in flavonols reduced the symptoms of food allergy upon challenge. Lee et al., 2010, Inflamm Res 59:847-854, disclose that specifically the flavonols quercetin and kaempferol suppress IgE mediated allergic inflammation in an in vitro system. Tea extracts have been studied for their efficacy in skin inflammation in animal models (Camouse et al., 2009, Exp Dermatol 18: 522-526). Further, Oolong tea, a traditional Chinese tea, is reported to have anti-allergic activities (Ohmori et al. 1995, Biol Pharm Bull 18: 683-686). Tea extracts are particularly rich in flavanols such as catechins, epicatechins and their derivatives. Epi-gallocatechin gallate (EPCG) was found to be the active ingredient in tea extracts that provide protection against cutaneous inflammation (Katiyar et al. 1995, Photochem Photobiol 62: 855-861).
The effect of polyphenols has also been investigated for respiratory allergies. Nauta et al., 2008, Eur J Pharmacol 585: 354-360) disclose the in vitro effect of green tea and some isolated polyphenols on allergic effector cells such as mast cells and basophils. Thereby, EGCG was identified as the effective inhibiting agent.
Usually, natural extracts of plant materials such as from apple or tea contain only small amounts of those active ingredients identified so far. This may make it difficult to practically apply those extracts to patients in need for example, of an effective daily dose.
Further, the choice of natural compounds isolated from food grade materials which demonstrate a potential for preventing or reducing allergic symptoms is still very limited. It would be an advantage to know more such compounds in order to compare and assess their individual activities, to optimize and strengthen the effects of compositions comprising such active compounds, and to ultimately provide solutions which can be part of a natural daily diet to patients in need.
There still remains a need to find new and alternative compounds to prevent and reduce the symptoms of an allergic disorder or allergic reaction, without some of the inconveniences as mentioned above and/or for complementing the already existing choice of active ingredients. Particularly, the new solution should not have adverse health or side-effects upon a prolonged consumption, and the compound should ideally be available from a natural source and in amounts, which would make it practical and feasible to be consumed by an individual for example as part of a daily diet in a high enough dose for being effective.